1. Field of the Invention
The present invention relates to a photolithography mask having monitoring marks and its manufacturing method. In particular, the invention relates to a photolithography mask that is suitable for correctly monitoring the dimensions of patterns that are intended for transfer, and to a manufacturing method of such a photolithography mask.
2. Description of the Background Art
Conventionally, for the purpose of measurement of pattern accuracy or the like, techniques are known which form a monitoring mark on a photolithography mask that is used in a semiconductor device manufacturing process. For example, if a monitoring mark having a prescribed design length value is formed on a mask and the length of the mark is measured actually, the accuracy of dimension of a pattern having the above prescribed design length value can be measured.
Incidentally, among known techniques of manufacturing a photolithography mask is a technique using an electron beam (EB) plotting apparatus. In this technique, the region on a mask is divided into a pattern region and a non-pattern region by electron beam plotting. Development etc. are performed thereafter, whereby a photolithography mask having desired patterns is formed.
In designing patterns to be formed on a mask, a data address unit that measures 50 nmxc3x9750 nm, for example, is used as a unit of designing. More specifically, patterns on a mask are designed by combining squares having a size that is represented by the data address unit.
On the other hand, the EB plotting apparatus plots patterns, to increase the throughput of a plotting step, while using as a unit of plotting an address unit whose side length is an integral multiple times longer than that of the data address unit (e.g., a square of 200 nmxc3x97200 nm). More specifically, patterns are plotted on a mask by irradiating the same with an electron beam by using, as a unit of plotting, a square having a size that is represented by the plotting address unit.
Therefore, in plotting a pattern on a mask, an edge of the pattern may coincide with edges of plotting address units or may not coincide with the latter. Specifically, in the above example, there occur the following four cases:
(1) A state that a pattern edge coincides with edges of plotting address units. Such an edge position will be hereinafter called a xe2x80x9cfirst edge position.xe2x80x9d
(2) A state that a pattern edge deviates inward (or outward) from edges of plotting address units by 50 nm (i.e., one data address unit). Such an edge position will be hereinafter called a xe2x80x9csecond edge position.xe2x80x9d
(3) A state that a pattern edge deviates inward (or outward) from edges of plotting address units by 100 nm (i.e., two data address units). Such an edge position will be hereinafter called a xe2x80x9cthird edge position.xe2x80x9d
(4) A state that a pattern edge deviates inward (or outward) from edges of plotting address units by 150 nm (i.e., three data address units). Such an edge position will be hereinafter called a xe2x80x9cfourth edge position.xe2x80x9d
Therefore, when mask patterns are formed by EB plotting, patterns having the same length (e.g., 1,000 nm) include the following plural kinds of patterns:
(1) A pattern having a pattern edge at a first edge position and having the prescribed length (1,000 nm). A plotting grid for plotting such a pattern will be hereinafter called xe2x80x9cGrid-1xe2x80x9d and such a pattern will be called a xe2x80x9cGrid-1 pattern.xe2x80x9d
(2) A pattern having a pattern edge at a second edge position and having the prescribed length (1,000 nm). A plotting grid for plotting such a pattern will be hereinafter called xe2x80x9cGrid-2xe2x80x9d and such a pattern will be called a xe2x80x9cGrid-2 pattern.xe2x80x9d
(3) A pattern having a pattern edge at a third edge position and having the prescribed length (1,000 nm). A plotting grid for plotting such a pattern will be hereinafter called xe2x80x9cGrid-3xe2x80x9d and such a pattern will be called a xe2x80x9cGrid-3 pattern.xe2x80x9d
(4) A pattern having a pattern edge at a fourth edge position and having the prescribed length (1,000 nm). A plotting grid for plotting such a pattern will be hereinafter called xe2x80x9cGrid-4xe2x80x9d and such a pattern will be called a xe2x80x9cGrid-4 pattern.xe2x80x9d
In plotting patterns with an EB plotting apparatus, four kinds of plotting grids (Grid-1 to Grid-4) are realized by properly controlling EB irradiation energy for each plotting address unit and the conditions of a subsequent development process. The EB irradiation energy and other process conditions are set properly for each plotting grid required. Therefore, the pattern edge position is prone to vary from one plotting grid to another. And the lengths of a Grid-1 pattern to a Grid-4 pattern are prone to be influenced by dispersion that depends on the kind of plotting grid.
However, conventional photolithography masks are not formed with a monitoring mark in such a manner that differences in pattern length due to the use of different plotting grids are taken into consideration. Therefore, in conventional photolithography masks, differences in pattern length due to the use of different plotting grids cannot be monitored even if the dimension of a monitoring mark is measured.
The present invention has been made to solve the above described problems in the art, and a first object of the invention is therefore to provide a photolithography mask having monitoring marks for monitoring differences in pattern length due to the use of different plotting grids.
A second object of the invention is to provide a manufacturing method of a photolithography mask having such monitoring marks.
The above objects of the present invention are achieved by a photolithography mask described below. The mask includes mask patterns that are designed on a data address unit basis. The mask also includes monitoring marks corresponding to all plotting grids, respectively, that are necessary in plotting the mask patterns by using a prescribed plotting address unit that is larger than the data address unit. Further, pattern edges that are plotted by using all different plotting grids are distributed to the monitoring marks, respectively.
The above objects of the present invention are also achieved by a photolithography mask described below. The mask includes a plurality of stripe regions having a prescribed width and formed in contiguous relation to each other. Each of the stripe regions corresponds to a unit for proceeding a plotting process. The mask also includes a plurality of on-boundary monitoring marks that overlap with a boundary line between a first stripe region and a second stripe region. The plurality of on-boundary monitoring marks are provided so that each on-boundary monitoring mark is different in the ratio between a portion formed in the first stripe region and a portion formed in the second stripe region from the other on-boundary monitoring marks.
The above objects of the present invention are further achieved by a manufacturing method of a photolithography mask having mask patterns that are designed on a data address unit basis. In the manufacturing method, the mask patterns are plotted by using a prescribed plotting address unit that is larger than the data address unit. There are plotted monitoring marks corresponding to all plotting grids, respectively, that are necessary for plotting of the mask patterns so that pattern edges that are plotted by using all different plotting grids are distributed to the monitoring marks, respectively.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.